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DN-009 L: Electrostatic properties of highland regolith at the lunar south pole

How South Pole regolith takes and holds charge: chargeability, volume and surface resistivity, and charge decay. "Electrostatics is one of the primary mechanisms in which lunar dust adheres to surfaces", so this data underpins dust mitigation. Today's design values rest on "limited Apollo data" and models. It is named in the Moon Base Users Guide (near-term), under six challenges, tied with DN-019 L for the most of any data gap (Data gaps spreadsheet, DN-009 L; Users Guide, pp. 12–13).

Quotations below are from row DN-009 L of the data gaps spreadsheet unless marked otherwise. ADD Rev C's Appendix E prints the same record as a table, and it matches the row field for field (ADD Rev C, p. 273).

Description

"Measure the state of the electrostatic charging level of granular materials. Electrostatic properties refer to the charge state of regolith at a given instance in time which is heavily dependent on the induced environment as well as the natural environment. Note that some electrostatic properties are intrinsic to the materials while others are not. Any disturbance of the regolith greatly affects the charge state. There are several types of electrostatics properties of interest including chargeability, volume and surface resistivity, and charge decay."

Need driver and data type

  • Need driver: Lunar Surface Natural Environment Characterization
  • Data type: In Situ Measurement

Target measurement parameters

"Measure several electrostatic properties of regolith such as chargeability, volume and surface resistivity, charge decay."

Current state of data

"Regolith electrical property values in M2M Design Specification for Natural Environments (DSNE) rely on limited Apollo data and estimates from analyses of orbital imagery or modelling. Variance in these values spatially and with terrain type is not well constrained."

Impact if data is unavailable

"Limitations in understanding of electrostatic properties can negatively impact effective design and employment of dust mitigation strategies and capabilities. Electrostatics is one of the primary mechanisms in which lunar dust adheres to surfaces. Without a detailed understanding of such properties and how external systems and factors may induce charge; dust can become a significant risk to surface elements and crew."

Benefits if data is available

"Increased confidence in development and performance of dust mitigation capabilities and better understanding of expected impacts on surface operations. Can help better plan mission operations that avoid accumulation of dust. Provide better understanding of potential near-surface natural dust transport/lofting."

Traceability

  • Objectives: AS-01 LM, LI-07 L, LI-08 L, TH-03 L, OP-05 LM (codes as printed; the sheet gives no titles)
  • Segment: Human Lunar Return (HLR): "The M2M segment during which the data is needed, but not necessarily when it is collected" (Data gaps spreadsheet, Key sheet). A segment is not a Moon Base phase.

Priority

None. The spreadsheet has no priority field, and the Users Guide calls the data-gap list "not comprehensive or prioritized" (Users Guide, p. 11).

Moon Base relevance

The Users Guide names DN-009 L for six challenges (Users Guide, pp. 12–13):

  • "Operating on the Lunar Surface for Long Durations" (headline challenge, p. 12). Its knowledge challenge has two sentences: "Characterize the lunar surface environment to predict performance impacts and risks associated with long duration surface operations." and "Investigate dust mechanics, regolith geotechnical properties, and radiation/charged particle fluctuations, seasonal patterns, and scattering." The guide lists DN-008 L to DN-013 L, DN-015 L, DN-016 L and DN-019 L under both sentences together and does not say which sentence each serves. The challenge's technology half cites tech gaps #0101, #0201, #0301, #0801 and #0804.
  • "Securing sites" (p. 12): "Identifying, selecting, and landing at individual sites requires more data about the lunar surface, including regolith properties, high-resolution imagery, mapping, and resource locations." Also cited: DN-001 L to DN-008 L, DN-010 L, DN-013 L and DN-014 L. No tech gap.
  • "Manipulating regolith" (p. 13): "Manipulating lunar regolith at scale for excavation, compaction, and site preparation requires in depth understanding of regolith properties and large scale excavation and construction." Also cited: data gaps DN-008 L, DN-010 L and DN-019 L; tech gaps #0505 and #0605.
  • "Electrical connections" (p. 13): "Connecting systems and sharing power on the lunar surface requires dust tolerant connections and the ability to deploy cables." Also cited: data gaps DN-008 L and DN-019 L; tech gap #0903.
  • "Wireless charging" (p. 13): "Demonstrating wireless charging for rovers requires both detailed knowledge of the lunar environment and interoperable wireless power systems that work in that environment." Also cited: tech gap #0903. DN-009 L is the only data gap cited here.
  • "Pressurized mating" (p. 13): "Mating pressurized systems on the lunar surface requires dust tolerant systems, which rely on detailed knowledge of lunar regolith and the surface environment." Also cited: data gaps DN-008 L, DN-010 L and DN-019 L; tech gap #0807.

The guide ties its challenges to "near-term Moon Base development efforts": missions in phase one "offer opportunities to collect data and mature technologies to enable essential phase two and phase three capabilities" (p. 11). See Technology and knowledge challenges.

Sources

Data gaps spreadsheet, DN-009 L · Users Guide, pp. 11–13 · ADD Rev C, p. 273